Method and system for optimizing a network by independently scaling control segments and data flow

ABSTRACT

A server array controller that includes a Data Flow Segment (DFS) and at least one Control Segment (CS). The DFS includes the hardware-optimized portion of the controller, while the CS includes the software-optimized portions. The DFS performs most of the repetitive chores including statistics gathering and per-packet policy enforcement (e.g. packet switching). The DFS also performs tasks such as that of a router, a switch, or a routing switch. The CS determines the translation to be performed on each flow of packets, and thus performs high-level control functions and per-flow policy enforcement. Network address translation (NAT) is performed by the combined operation of the CS and DFS. The CS and DFS may be incorporated into one or more separate blocks. The CS and DFS are independently scalable. Additionally, the functionality of either the DFS or the CS may be separately implemented in software and/or hardware.

RELATED APPLICATION

[0001] This application claims the benefit under 35 U.S.C. § 119(e) ofU.S. Provisional application Ser. No. 60/191,019, filed Mar. 21, 2000.

FIELD OF THE INVENTION

[0002] The present invention relates to a method and apparatus forcontrolling the flow of data in a network. More specifically, thepresent invention relates to a network controller that is partitionedinto a software controller section and a hardware controller section,the hardware controller section communicating with the softwarecontroller section to control the switching of data flow.

BACKGROUND OF THE INVENTION

[0003] Local area networks (LANs), which were once merely a desirabletechnology available to share common network resources, are now anintegral part of any information technology (IT) infrastructure.Moreover, the concept of the LAN has expanded to the wide area network(WAN), where remote offices and databases are made available to LANclients as through they are connected to the same LAN. More recently,virtual private networks (VPN) have been utilized to allow a privateintranet to be securely extended across the Internet or other networkservice, facilitating secure e-commerce and extranet connections withpartners, suppliers and customers. The evolution of global networkinghas rapidly advanced networking topologies.

[0004] LAN segments are routinely connected together using a bridgedevice. The bridge device allowed the two network segments to sharetraffic despite differences in the network topologies. For Example, aToken Ring network and an Ethernet network can share network trafficusing a bridge device.

[0005] Routers became popular to couple one LAN to another LAN or WAN.Routers store data packets from one LAN and forward those data packetsto another LAN or WAN. The need for faster communication resulted in thedevelopment of the high-speed switch, also referred to as a layer 2/3switch. High-speed switches move data packets across a network to an enduser.

[0006] When client-server networks first emerged, servers were generallyplaced close to their clients. As the applications delivered overnetworks became more advanced, the servers increased in complexity andcapacity. Moreover, applications that ran over these networks such ase-mail, intranet web sites, and Internet gateways, became indispensablypervasive. Supporting these services became critically important, andproved far too complex when servers were widely distributed within theenterprise. As a result, it has become a standard practice toconsolidate such resources into server arrays.

[0007] A Server array controller is an Internet traffic managementdevice. Server array controllers (hereinafter referred to simply a“controller” or “controllers”) control the flow of data packets in andout of an array of application servers. The controller manages anddistributes Internet, intranet and other user requests across redundantarrays of network servers, regardless of the platform type. Controllerssupport a wide variety of network applications such as web browsing,e-mail, telephony, streaming multimedia and other Internet protocol (IP)traffic.

[0008] Although advances in data communication technology havedramatically improved the transmission speeds, many problems stillexist. Application availability can still be threatened by contentfailure, software failure or server failure. System resources are oftenout of balance, with low-performance resources receiving more userrequests than high-performance resources being underutilized. InternetTraffic Management (ITM) products are computer systems that sit in thenetwork and process network traffic streams. ITM products switch andotherwise respond to incoming requests by directing them to one of theservers.

[0009] A more complete appreciation of the invention and itsimprovements can be obtained by reference to the accompanying drawings,which are briefly summarized below, to the following detail descriptionof presently preferred embodiments of the invention, and to the appendedclaims.

SUMMARY OF THE INVENTION

[0010] In accordance with the invention, an apparatus is provided fordirecting communications over a network. A control component receives adata flow requesting a resource and determines when the data flow isunassociated with a connection to a requested resource. When the controlcomponent determines that the data flow is unassociated with theconnection to the requested resource, it will associate a selectedconnection to the requested resource. A switch component employs theconnection associated with the data flow to direct the data flow to therequested resource. The capacity of the switch component and thecapacity of the control component are independently scalable to supportthe number of data flows that are directed to requested resources overthe network.

[0011] In accordance with other aspects of the invention, the controlcomponent employs a buffer to list each data flow that is associatedwith the connection to the requested resource. The control component canemploy a table to list each data flow associated with the connection tothe requested resource. Also, the control component may categorize aplurality of data packets for each data flow. Additionally, the controlcomponent can determine when an event associated with the data flowoccurs and categorize each event.

[0012] In accordance with other additional aspects of the invention, aflow signature is associated with the data flow. The flow signature iscompared to a set of rules for handling each data flow that isassociated with the connection to the requested resource. The flowsignature includes information about a source and a destination for eachdata packet in the data flow. Also, the flow signature can include atimestamp.

[0013] In accordance with still other additional aspects of theinvention, the switch component collects metrics regarding eachconnection to each resource. Additionally, a server array controller canact as the control component and the switch component.

[0014] In accordance with yet other additional aspects of the invention,the invention provides for directing communications over a network. Aflow component receives packets associated with a flow and switches eachreceived packet associated with the flow to a connection. A controlcomponent determines the connection based on information collected bythe flow component. The flow segment and the control segment areindependently scalable to handle the number of data flows that aredirected to requested resources over the network.

[0015] In accordance with other additional aspects of the invention, thecontrol component performs control and policy enforcement actions foreach flow. Also, the control component collects information regardingeach flow including metrics and statistics. The control componentperforms load balancing for each flow based on the information collectedby the flow component. Additionally, a primary control component and asecondary control component can share a load. When the primary controlcomponent is inoperative, the secondary control component can take overthe actions of the primary control component and the flow componentprovides the state information for each flow.

[0016] In accordance with still other additional aspects of theinvention, a server array controller includes the control component andthe flow component. Also, the server array controller includes aninterface for internal and external networks.

[0017] In accordance with yet other additional aspects of the invention,a flow signature is associated with each flow. A timestamp is associatedwith each flow; and the control component employs the timestamp todetermine factors used for load balancing. These factors include mostactive, least active, time opened and most recent activity. Also, asession that is associated with the flow can include the TCP and UDPprotocols. Additionally, the control component can determine when a newflow occurs based on the detection of an event.

[0018] In accordance with other additional aspects of the invention, amethod is provided for directing communications over a network,including (a) employing a control component to receive a data flowrequesting a resource; (b) determining when the data flow isunassociated with a connection to a requested resource; (c) When thedata flow is unassociated with the connection to the requested resource,associating a selected connection with the requested resource; and (d)employing the connection associated with the data flow to switch thedata flow to the requested resource. Additionally, the switchingcapacity and the control capacity are independently scalable to supportthe number of data flows that are directed to requested resources overthe network.

[0019] In accordance with yet other additional aspects of the invention,sending state information as multicast messages and other information aspoint cast messages. Also, responding to messages that areauthenticated. Additionally, employing a state sharing message bus(SSMB) between a switch and a control component. The SSMB can be layeredon top of a session that may include the TCP and UDP protocols. Further,asynchronous and independent communication may occur between the controlcomponent and the switch.

[0020] In accordance with still other additional aspects of theinvention, associating a flow signature with each flow. Also, comparingwhen the data flow is associated with the connection to the requestedresource and when the interface component determines that the data flowis unassociated with the connection to the requested resource. Thecomparison is employed to determine the data flow's association with theconnection to the requested resource.

[0021] The present invention may be implemented as a computer process, acomputing system or as an article of manufacture such as a computerprogram product or computer readable media. The computer program productmay be a computer storage media readable by a computer system andencoding a computer program of instructions for executing a computerprocess. The computer program product may also be a propagated signal ona carrier readable by a computing system and encoding a computer programof instructions for executing a computer process.

[0022] These and various other features as well as advantages, whichcharacterize the present invention, will be apparent from a reading ofthe following detailed description and a review of the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023]FIG. 1 is a system diagram of an exemplary partitioned controller;

[0024]FIG. 2 is a system diagram of an exemplary partitioned controllerincluding connections to a client and server;

[0025]FIG. 3 is an exemplary diagram of packet flows from client toserver in a partitioned controller;

[0026]FIG. 4 is a table of mnemonics used in an exemplary partitionedcontroller;

[0027]FIG. 5 is a chart showing message fields used in an exemplarypartitioned controller;

[0028]FIG. 6 is a table showing message contents used in an exemplarypartitioned controller;

[0029]FIG. 7 is a chart showing Boolean variables used in an exemplarypartitioned controller;

[0030]FIG. 8 is a chart showing error codes used in an exemplarypartitioned controller;

[0031]FIG. 9 is a diagram of formatted message packets using the messagefields and variables shown in FIGS. 5 and 6;

[0032]FIG. 10 is another table of mnemonics used in an exemplarypartitioned controller;

[0033]FIG. 11 is another chart showing message fields used in anexemplary partitioned controller;

[0034]FIG. 12 is another table showing message contents used in anexemplary partitioned controller;

[0035]FIG. 13 is a chart describing server classes in an exemplarypartitioned controller;

[0036]FIG. 14 is a diagram of formatted message packets using themessage fields and variables shown in FIGS. 10 and 11;

[0037]FIG. 15 is another chart of Boolean variables used in an exemplarypartitioned controller;

[0038]FIG. 16 is another chart of error codes used in an exemplarypartitioned controller;

[0039]FIG. 17 is a flow chart of basic operations for a data flowsegment (DFS) in an exemplary partitioned controller;

[0040]FIG. 18 is a flow chart of flow activity management for a dataflow segment (DFS) in an exemplary partitioned controller;

[0041]FIG. 19 is a flow chart of flow activity management for a controlsegment (CS) in an exemplary partitioned controller;

[0042]FIG. 20 is a flow chart of message processing for a data flowsegment (DFS) in an exemplary partitioned controller;

[0043]FIG. 21 is a flow chart of new flow management for a data flowsegment (DFS) in an exemplary partitioned controller; and

[0044]FIG. 22 is a flow chart of message processing for a controlsegment (CS) in an exemplary partitioned controller in accordance withthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0045] An embodiment of the invention relates to segmenting part of aserver array controller into hardware-optimized and software-optimizedportions. The server array controller (controller) performs loadbalancing and other traffic control functions. An illustration of aserver array controller that is segmented in accordance with the presentinvention is shown in FIG. 1.

[0046] The server array controller (hereinafter referred to simply as a“controller”) shown in FIG. 1 includes one or more network interfaces,and performs the operations of routing, translating, and switchingpackets. Although FIG. 1 includes an internal and external networkconnection, a single network connection is also within the scope of thepresent invention. The controller maintains the state of each flow ofpackets. The controller dynamically selects operations on “flows” basedon the content of the packets in the flow. A flow is a sequence ofpackets that have the same flow signature.

[0047] A flow signature is a tuple including information about thesource and destination of the packets. In one example, the flowsignature is a sextuple of source IP address, source port number,destination IP address, destination port number, protocol, andtype-of-service packets in a flow. A flow exists for a finite period.Subsequent flows may have the same flow signature as a previouslyreceived flow.

[0048] In accordance with invention, the controller includes a Data FlowSegment (DFS) and at least one Control Segment (CS). The DFS includesthe hardware-optimized portion of the controller, while the CS includesthe software-optimized portions. The DFS performs most of the repetitivechores including statistics gathering and per-packet policy enforcement(e.g. packet switching). The DFS may also perform tasks such as that ofa router, a switch, or a routing switch. The CS determines thetranslation to be performed on each flow of packets, and thus performshigh-level control functions and per-flow policy enforcement. Networkaddress translation (NAT) is performed by the combined operation of theCS and DFS.

[0049] Although the server array controller is shown as two partitions,it is understood and appreciated that the segmented blocks may beincorporated into one or more separate blocks including, but not limitedto, two segments in the same chassis, each CS is a module that plugsinto the DFS chassis, and the two segments are merely functional blocksin the same server array controller. The CS and DFS are independentlyscalable. In one example, multiple DFSs cooperate with a single CS. Inanother example, multiple CSs cooperate with a single DFS. Additionally,it is envisioned that the functionality of either the DFS or the CS maybe separately implemented in software and/or hardware.

[0050] The DFS includes at least one connection to a network that can beexternal or internal. An external network connection is typically to theclient-side of the network. The external network is said to be “in frontof” the controller. An internal network connection is typically to theserver-side of the network, which may include routers firewalls, caches,servers and other devices. The internal network is said to be “behind”the controller. Network address translation normally occurs between theinternal and external networks.

[0051] Any number of control segments may be coupled to the DFS over themessage bus (see FIG. 1). Typically, there is a primary CS and asecondary (or redundant) CS. Multiple control segments allow for loadsharing between the control segments. In addition, fault tolerance isprovided for since the primary CS can go out of service while thesecondary CS assumes the role of the primary control segment. An exampleconfiguration with two control segments is shown in FIG. 2.

[0052] As shown in FIG. 2, a client (C1) is connected to an input port(1) of a data flow segment (DFS) through the Internet (externalnetwork). A first control segment (CS1) is connected to the DFS throughports 2 and 3 (INT and EXT). A second control segment (CS2) is connectedto the DFS through ports 7 and 8 (INT and EXT). Content servers (N1, N2,N3) are connected to ports 4, 5 and 6. The content servers are behindthe controller on the internal network.

[0053] A client communicates from the external network to the internalnetwork through the DFS. The DFS communicates with the various controlsegments for instructions on new flows. The CS can access the networksthat are connected to the DFS. The networks that are connected to theDFS may be of any type such as, for example, Fast Ethernet and GigabitEthernet. Administration and state sharing (if applicable) are providedover the messaging bus by either the internal or external interfaces (orboth). Although the control segments are shown requiring two ports (EXTand INT), it is understood and appreciated that a single port connectionwill serve equally well.

[0054] The DFS categorizes packets into flows and performs translationson the packets in each flow. Translation is a set of rules that controlwhich parts of a packet are to be rewritten, and the values that thoseparts will be rewritten to. Packets can be received by the DFS from bothinternal and external networks. After the packets are received, the DFScategorizes the packets into flows, analyzes the flow signature, andlooks up the rules for that flow signature in a table (or anothersuitable data construct). If the table does not have an entry for theparticular flow signature, the DFS sends a query to the CS over themessage bus for instructions. The CS replies with instructions onhandling the new flow, and the DFS makes a new rule entry in the tablefor the new flow signature. The DFS routes, switches or otherwisedirects the flow based on the rules for the particular flow signature.Thus, the DFS has capabilities that are similar to that of a router, aswitch, or a routing-switch.

[0055] The DFS also detects certain events that occur for each flow.When an event that falls into a particular category (e.g. open a newconnection) is detected, a message is sent from the DFS to the CS. TheCS immediately responds with a message that describes translations andswitching to perform on the flow (if required). The operation of the DFSwill become apparent from the discussion that follows below.

[0056] A virtual server is an IP address and TCP/UDP port combination(the actual server is referred to as a “node”). The controller accepts arequest from the virtual server and load balances those requests toservers situated behind the controller. Virtual servers are establishedby the CS and communicated to the DFS via the message bus. The DFSattempts to match the destination address and port number of packetsreceived from the external network to a virtual server.

Overview of the Operation of the DFS

[0057]FIG. 3 shows a conceptual operation of an example scenario inwhich a client and a server exchange sequences of packets.

[0058] First, a client sends a first packet to the DFS. The DFS receivesthe packet and determines that the packet is not part of any flowcurrently being maintained. The DFS sends a message (QUERY) to the CSrequesting instructions on how to handle the new flow (i.e which servershall packets be routed to). The CS receives the message from the DFS,determines how to handle FLOW A, and sends a message (REPLY) to the DFSwith instructions on how to handle the flow. The DFS receives themessage (REPLY) from the CS and stores the instruction in a local memory(table, etc.). Then, the DFS begins to process the packets for FLOW Aand send the processed packets to the selected server.

[0059] A set of packets is sent from the server to the client inresponse to the server receiving FLOW A (i.e. a handshake, acknowledge,etc.). The server sends the packets to the DFS. The DFS receives thepackets from the server and recognizes the packets as belonging to areturn flow (FLOW B) of an existing communication by FLOW A. The DFSprocesses the packets and sends the processed packets to the selectedclient without intervention by the CS.

[0060] The client sends another set of packets to the DFS. The DFSreceives the packets immediately recognizes that the packets belong toan existing flow (FLOW A). The DFS processes the packets and sends theprocessed packets to the selected server without intervention by the CS.

[0061] After receiving packets corresponding to FLOW A, the serverresponds by sending packets to the DFS. The DFS receives the packetsfrom the server and recognizes the packets as belonging to an existingflow (FLOW B). The DFS processes the packets and sends the processedpackets to the selected client without intervention by the CS.

[0062] The present invention may be implemented with varying wireprotocols. Each wire protocol defines a communication protocol formessage exchanges between the DFS and the CS (or multiple CSs). Althoughtwo different wire protocols are discussed below, any other suitablewire protocol is considered within the scope of the present invention.

SSMB Wire Protocol (Real Time Configuration Protocol)

[0063] In one example of the present invention, the messaging bus isstructured as a state-sharing message bus (SSMB). The SSMB operates inreal-time, has extremely low latency, and high bandwidth. Since thetotal latency of the controller includes the round-trip latency of theSSMB interface, it is important that the SSMB have low latency and ahigh bandwidth to provide adequate real-time operation. The SSMB busstructure is useful for systems where the DFS actively sends andreceives messages to/from the CS (or multiple CS).

[0064] In one embodiment, the SSMB is layered on top of UDP. All messagetypes fit into one UDP data-gram. Also, all message types should fitwithin on MAC frame to avoid IP fragmentation and reassembly.

[0065] The flow of messages from CS to DFS is asynchronous andindependent of the flow of messages from the DFS to CS. Reply messagesare initiated in response to query messages. The request and repliesfrom the DFS and CS need not be interleaved. The querying segment shouldnot be idle while waiting for a reply. The querying segment should notwaste time trying to associate received replies with queries. Instead,reply messages should be self-contained so that the receiving segmentwill process the reply without needing to know what the original querywas.

[0066] Each message contains a serial number (or other indicator) thatis generated by the originator of the flow. The originator of the flowis the first party to query or notify the other party regarding theflow. The serial number remains constant for all messages pertaining tothe flow during the flow's lifetime. Since the DFS is typically thefirst party to detect an inbound flow (from the external network to theinternal network), the DFS is generally the originator of the flow. Inthis case, the DFS sends a message (QUERY) to the CS to notify the CSabout the new flow. In some instances (e.g. CS-assisted flow), the CSoriginates the flow by sending a message (NEWFLOW) to the DFS.

[0067] In one example of the present invention, message types aredefined as depicted in table I shown in FIG. 4. A “Y” entry in the “DFSSends?” column indicates that the message is sent from the DFS to the CS(or multiple CSs). A “Y” in the “CS Sends?” column indicates that themessage is sent from the CS to DFS. An “H” priority indicates a timecritical message, usually because the latency of packets in a flow isproportional to the time for the message and it's reply. An “L” priorityindicates that the message is not a time-critical message. A “Y” in the“Batching?” column indicates that the information portion of the messagemay be combined with other messages such that the messages are sent as abatch. A “Y” in the “Single mbuf?” column indicates that the message isrequired to fit in a single memory buffer of the DFS or CS as isapplicable. A “Y” in the “State Sharing” column indicates that themessage is to be replicated to the standby CS (or multiple CSs) if thereis one. The “Expected Response” column indicates the type of messagethat is expected in response to the current message.

[0068]FIG. 5 shows a table (table II) listing the data elements that areexpected to be sent in a given message. Each message type may consist ofa predefined subset of these data elements. The length of the message isderived from the UDP header.

[0069]FIG. 6 shows a table (table III) of message fields for the messagetypes defined in FIG. 4. After having read the present disclosure, it isunderstood and appreciated that other message types and message fieldsmay also be utilized within the scope of this invention. The messagelayout is optimized for efficient processing by the CS and according tothe needs of the particular DFS. Every message has a message header thatincludes msg_type, error_code, and message serial number fields. Examplemessage layouts are shown in FIG. 9.

[0070]FIG. 7 shows a table of exemplary boolean variables that arepacked into the flags field shown in FIG. 6. The OUTBOUND variabledetermines if a message concerns an inbound flow or an outbound flow(TRUE=outbound, FALSE=inbound). The majority of messages are regardinginbound flows. The ADD_TCP_OFFSETS variable determines if the TCP packetis to be offset or not (TRUE=offset TCP packet, FALSE=do not offset TCPpacket). When an offset is to be added to the TCP packet, the seq_offsetand ack_offset variables are used to determine the amount of offset tobe added to the values found in the TCP header. TCP packets are oftenoffset when the TCP handshake proxy is performed by the CS.

[0071]FIG. 8 shows a table of exemplary error codes that are used in theerror field shown in FIG. 6. A code of UNKNOWN indicates that the CSdoes not know how to handle a particular flow. A code of NOTAVAILindicates that the virtual server that was requested in a QUERY messageby the DFS is not available because either the port requested was deniedor the virtual server is in maintenance mode. A CONNLIMIT error codeindicates that the requested connection (in a QUERY from the DFS) wouldexceed the maximum available connections to the virtual server. ACONNALIVE error code indicating that a flow subject to a SSMB REAPmessage (requesting deletion of a flow) from the CS is still active. TheDFS sends a STATS message with this error field set to request the CS toincrease the statistics on the flow.

[0072] When a redundant CS topology is used, one CS is the primary(active) controller, and the remaining CS (or multiple CSs) is a backupor standby controller. The standby CS receives copies of all stateinformation originating in the active CS. Specifically, the standby CSneeds to receive a copy of any state information message that iscommunicated by the active CS to the DFS so that all of the CSs sharecommon state information. Exemplary state information messages are shownin FIG. 6.

[0073] The DFS is designed to facilitate shared state information acrossmultiple control segments (CSs) using any appropriate communicationmethod including, but not limited to, IP multicasting and artificialpacket replication.

[0074] An IP multicast message joins all control segments (CSs) and theDFS into a common IP multicast group. The active CS sends all stateinformation messages as multicast messages. The DFS receives themulticast message, replicates the message, and sends the replicatedmessage to all members of the IP multicast group. All othernon-multicast messages are pointcast on a separate non-multicastaddress.

[0075] For certain DFS implementations, an artificial packet replicationmethod is simpler to implement than IP multicast messaging. The effectof artificial packet replication is the same as multicast in that theDFS creates a replica of the received state information and forwards acopy of the state information to the standby control segment(s).However, the active CS is not required to send the information to theDFS as a multicast message as in the IP multicast message method.

[0076] The CS will not respond to an SSMB message unless the DFS hascorrectly responded to an authentication challenge. The format for anauthentication message is shown in FIG. 6 and FIG. 9. Authenticationwill be discussed in further detail as follows below in thisspecification.

CSMB Wire Protocol

[0077] Another type of messaging bus structure is a configurationsharing message bus (CSMB). The CSMB works in concert with the SSMB WireProtocol. The CSMB does not need to operate in real-time. In oneexample, the CSMB is layered on top of TCP. The protocol is carried byone or both of the network connections between the CS and the DFS.

[0078] The DFS passively monitors the message bus. The CS actively makesconnections, while the DFS accepts connections. The CS automaticallyconnects whenever it detects that it is not already connected. The DFSsupports simultaneous connections between the DFS and multiple controlsegments (CSs).

[0079] Whenever a new connection is established the CS (or multiple CSs)and the DFS send HELLO messages (e.g. see FIG. 10) to one another priorto any other message types. The CS will also periodically send a HELLOmessage to the DFS to validate the connection. The CS configures thetime interval between the transmissions of HELLO messages.

[0080] The CSMB wire protocol provides for an asynchronous flow ofmessages from the CS (or multiple CSs) to the DFS. The flow of messagesfrom the CS to the DFS is independent of the flow of messages from DFSto CS. Reply messages are initiated in response to query messages. Therequests and replies from the DFS and CS need not be interleaved. Thequerying segment should not be idle while waiting for a reply. Thequerying segment does not waste time trying to associate receivedreplies with queries. Instead, reply messages are self-contained so thatthe receiving segment will process the reply without needing to knowwhat the original query was.

[0081] Each message contains a serial number (or other indicator) thatis global for all messages, and a serial number that is specific tomessages of the specific type. In one embodiment the serial numbers areunsigned 16-bit integers.

[0082] According to one embodiment of the invention, message types aredefined in a table (table IV) as shown in FIG. 10. A “Y” entry in the“DFS Sends?” column indicates that the message is sent from the DFS tothe CS (or multiple CS). A “Y” in the “CS Sends?” column indicates thatthe message is sent from the CS to DFS. The “Expected Response” columnindicates the type of message that is expected in response to thecurrent message.

[0083]FIG. 11 is a table (table V) listing data elements that areexpected to be sent in a given message. Each message type may consist ofa predefined subset of these data elements. The length of the message isderived from the UDP header.

[0084]FIG. 12 shows a table (table VI) of message fields for the messagetypes defined in FIG. 10. It is understood and appreciated that othermessage types and message fields may also be utilized within the scopeof this invention. The message layout is optimized for efficientprocessing by the CS and according to the needs of the particular DFS.Every message has a message header that includes msg_type,serial_global, serial_bytype and msg_length fields. Example messagelayouts are shown in FIG. 14.

[0085] Version number fields (vers_major, vers_minor) apply to both CSMBand SSMB wire protocols. In the HELLO messages (see FIGS. 12 and 14),the CS and DFS attempt to negotiate the highest numbered version that issupported by both.

[0086] Two different virtual server classes are supported, a CS-assistedvirtual server and a DFS-assisted virtual server (see FIG. 13). Virtualservers that do not require application data load balancing are of theclass DFS_ASSIST. The DFS-assisted virtual server has no special flagsettings in the ADD_VS and VS_LIST messages.

[0087] As discussed previously, virtual servers (defined as an IPaddress and TCP/UDP port combination) are established by the CS andcommunicated to the DFS via the message bus. For CSMB wire protocol, theCS is configured to automatically inform the DFS of each deletion andaddition of virtual servers.

[0088] The controller accepts a request from the virtual server(sometimes referred to as a “node”) and load balances those requests toservers situated behind the controller. The DFS attempts to match thedestination address and port number of packets received from theexternal network to a virtual server.

[0089] In one embodiment of the invention, the DFS performs TCPhandshake proxy (also referred to as TCP splicing) for certain types ofvirtual servers, and also extracts application specific data from theclient request. The DFS sends a message to the CS that includes theextracted data (SSMB APP_QUERY, see FIGS. 6 and 9). Virtual servers thatare supported according to this embodiment are of the class DFS_ASSIST.These virtual servers are specified using the ADD_VS and VS_LISTmessages (see FIGS. 10, 12 and 14). Setting the flags for SSL_PROXY,HTTP_PROXY, specifies the DFS_ASSIST type virtual servers orCOOKIE_PROXY, as will be discussed later.

[0090] In another embodiment of the invention, the DFS does not have thecapability to extract application data from the client request becauseit is an unsupported application protocol. In this instance, the DFSwill perform the TCP handshake proxy with the client and forward(bridge) a copy of the client packets to the CS (or multiple CSs).Virtual servers that are supported according to this embodiment are ofthe class DFS_ASSIST. These virtual servers are specified using theADD_VS and VS_LIST messages (see FIGS. 10, 12 and 14). Setting the flagsfield to RAW_PROXY (discussed later) specifies the DFS_ASSIST type forunsupported application protocols.

[0091] Virtual servers may also be of the class CS_ASSIST, where the CSroutes all packets in a flow that are related to a specific CS assistedvirtual server. In this instance, the DFS bridges all packets to andfrom the CS, and state or configuration data is not exchanged betweenthe DFS and the CS. The CS_ASSIST class of virtual servers is used whenthe DFS is incapable of performing the TCP handshake proxy. TheCS_ASSIST class of virtual servers is also used when the DFS isincapable of assuming a flow from the CS using a hybrid CS assistedvirtual server.

[0092] A hybrid CS assisted virtual server is used in conjunction withthe TCP handshake proxy. Flows begin as CS_ASSIST and then switch overto DFS_ASSIST after the TCP handshake proxy is complete and a message(NEWFLOW) is received from the CS. For TCP flows, the DFS adds thesequence number and ack offsets received in the NEWFLOW message to allthe packets received in the flow.

[0093]FIG. 15 shows a table of exemplary Boolean variables that arepacked into the flags field shown in FIG. 12. The TRANSLATE ADDRvariable determines if the DFS will provide address translationfunctions for an incoming flow (TRUE=translate, FALSE=do not translate).The TRANSLATE_PORT variable determines if the DFS will provide porttranslation functions for an incoming flow (TRUE=translate, FALSE=do nottranslate). The ROUTE_BY_DST_IP variable determines if the DFS willperform a route address lookup (TRUE) or if the DFS will use thenext_hop_ipaddr field to determine the next hop for the flow (FALSE).

[0094] The REDUNDANT and APP_PROXY variables are part of the HELLOmessage. When REDUNDANT is set to TRUE, multiple CSs are used and thessmb_standby_ipaddr is used for state sharing. When state sharing is notused or multiple CSs are not used, the REDUNDANT variable is set toFALSE. When the WILDCARD_ADDR variable is set to TRUE, the virt_ipaddrfield is ignored and all traffic received from the external network thatis destined for any address that does not match another virtual serveror other known local address is processed as if it was addressed to thisvirtual server. When the WILDCARD PORT variable is set to TRUE, thevirt_port field is ignored and all traffic received that is destined forany virtual port that does not match the virtual port of any othervirtual server is processed as if it was addressed to this virtualserver. If the NOARP_MODE is set to TRUE then the controller acts like arouter and accepts packets destined to the address but does not respondto ARP requests for the address. When NOARP_MODE is set to FALSE, thecontroller acts as a host and advertises the address (e.g., responds toARP requests). When APP_PROXY is set to TRUE, the controller supportsapplication data load balancing, and can perform the TCP handshake proxyas well as extract application data from the client request. The CStypically sets APP_PROXY to TRUE. The DFS set APP_PROXY to TRUE if theDFS has sufficient capability to do so. If SSL_PROXY is set to TRUE thenthe CS makes load-balancing decision for the virtual server based uponthe client's SSL session id. The DFS proxies the client connection,extracts the session id, and sends the session id to the CD. IfCOOKIE_PROXY is set to TRUE then the CS makes load-balancing decisionsfor the virtual server based upon the value of a cookie in the HTTPrequest. The DFS proxies the client connection, extracts the designatedcookie, and send the cookie to the CS with the cookie name provided inthe app_data field. If HTTP_PROXY is set to TRUE then the CS makesload-balancing decisions for the virtual server based upon the value ofthe HTTP request. The DFS proxies the client connection, extracts theHTTP request, and sends the data to the CS. If RAW_PROXY is set to TRUEthen the CS makes load-balancing decisions based upon an applicationdata format that is not supported by the DFS. The DFS proxies the clientconnection and bridges packets that are received from the client to theCS.

[0095]FIG. 16 shows a table of exemplary error codes that are used inthe error field shown in FIG. 12. A code of VERS_NEW indicates that theparticular segment does not yet support the version specified in theHELLO message. If possible, the other segment should send another HELLOmessage with a lower version number. A code of VERS_OBSOLETE indicatesthat the particular segment no longer supports the version specified inthe HELLO message. In this case, the other segment should send anotherHELLO message with a higher version number.

[0096] In one embodiment of the invention, CSMB messages are used tonegotiate IP addresses and UDP port numbers for the SSMB wire protocol.CSMB may also be used to exchange configuration information such as thedefault gateway address and other administrative IP addresses. CSMB isalso used to negotiate versions between the CS and DFS for both the SSMBand CSMB wire protocols.

[0097] The CS sends authentication challenges to the DFS using the CSMBwire protocol. The CS also sends other messages to the DFS such as theaddition or deletion of each virtual server. The CS will not respond toa CSMB message from the DFS unless the DFS has correctly responded to anauthentication challenge. The format for an authentication message isshown in FIG. 12 and FIG. 9. Authentication will be discussed in furtherdetail as follows below in this specification.

Operation of the DFS in SSMB Mode

[0098]FIG. 17 shows a flow chart of the basic operation of the DFS.Processing begins at start block 1710 and proceeds to block 1720 wherethe DFS waits for the receipt of a new packet. When a new packet isreceived, processing proceeds to block 1730. Proceeding to block 1740,the DFS analyzes the new packet to determine if the packet is part of anew flow.

[0099] When the incoming packet is part of an existing flow, processingproceeds to block 1770 where the incoming packet is processed andsubsequently sent to the selected client or server as may be required.Processing then proceeds to block 1720 where the DFS waits for thereceipt of another packet.

[0100] Returning to decision block 1740, when the incoming packet isidentified as part of a new flow, processing proceeds to block 1750where the DFS sends a message (QUERY) to the CS for instructions onhandling the new flow. Processing then proceeds from block 1750 to block1760 where the DFS receives an instruction from the CS (REPLY) on how tohandle the new flow. The DFS then stores the instruction from the CS ina local memory area (i.e. a table). Once the DFS has stored theprocessing instructions, processing proceeds to block 1770 whereincoming packets are processed and the packets are sent to the selectedclient or server (as is required).

[0101] Although the processing is shown as sequential in FIG. 17, theDFS continually receives packets and messages from the CS in anasynchronous manner. Since the DFS is continually receiving packets andmessages, the DFS may not enter an idle state and continues processingmessages and packets from a local memory buffer.

Flow Management

[0102] As discussed previously flows have a finite lifetime. The DFS andCS have different notions concerning when an existing flow ends. The DFSand CS have independent creation and deletion of flows.

[0103] An overview of the operation of the DFS procedure that is used todetermine if a flow is still alive is shown in FIG. 18. Processingbegins at start block 1810 and proceeds to decision block 1820 where theDFS determines if a TCP shutdown (FIN or RST) is detected within theflow. When a TCP shutdown is detected within the flow, processingproceeds to block 1860 where the flow is deleted.

[0104] Returning to decision block 1820, when the DFS determines thatthe flow does not contain a TCP shutdown, processing proceeds todecision block 1830 where the DFS determines if an overflow has occurredin a flow table (DFS flow table). As discussed previously, the DFSmaintains a table that keeps track of each flow signature and rules forprocessing each flow. When the table no longer has enough room toaccommodate additional entries, an overflow condition occurs. When theoverflow condition has occurred, processing proceeds from decision block1830 to block 1860 where the flow is deleted.

[0105] Returning to decision block 1830, when the DFS determines thatthe flow table has not overflowed, processing proceeds to decision block1840 where the DFS determines if a flow timeout has occurred. When thetimeout condition has occurred, processing proceeds from decision block1840 to block 1860 where the flow is deleted.

[0106] Returning to decision block 1840, when the DFS determines thatthe flow timeout has not occurred and processing proceeds to block 1850where the DFS determines that the flow is still alive. From block 1850,processing proceeds to block 1870 where the flow management for the DFSis complete. In one embodiment of the invention, the DFS sends a messageto the CS to inform the CS that the flow is still active. In anotherembodiment of the invention, all messages that are sent from aparticular CS are monitored by all CSs so that each CS may maintainduplicate table entries for fault tolerance.

[0107] As described above, the DFS deletes flows when: a normal TCPshutdown (FIN or RST) is detected within the flow, an overflow in theflow table occurs, or a timeout for the flow has expired. The DFS alsodeletes flows when the CS has sent a REAP or TIMEOUT message about theflow and the DFS does not consider the flow to be active.

[0108] An overview of the operation of the CS procedure that is used todetermine if a flow is still alive is shown in FIG. 19. Processingbegins at start block 1910 and proceeds to decision block 1920 where theCS determines if a TCP shutdown (FIN or RST) is detected within theflow. When a TCP shutdown is detected within the flow, processingproceeds to block 1950 where the flow is deleted.

[0109] Returning to decision block 1920, when the CS determines that theflow does not contain a TCP shutdown and processing proceeds to decisionblock 1930 where the DFS determines if a flow timeout has occurred. Whenthe timeout condition has occurred, processing proceeds from decisionblock 1930 to block 1950 where the flow is deleted. Otherwise, if noflow timeout has occurred, processing proceeds from decision block 1930to block 1940 where the CS determines that the flow is active.

[0110] In one embodiment of the present invention, the CS sends amessage to the DFS (e.g. REAP) when the CS has determined that a flowshould be terminated due to inactivity. If the DFS determines that theflow is still active, the DFS sends a message (e.g. STATS) to the CSthat includes an error code indicating the flow is still alive (e.g.CONNALIVE). When the CS receives the STATS message indicating a flow isactive, the CS will not delete the flow and will reset the inactivitytimer for the flow.

[0111] As discussed previously, the CS performs high-level controlfunctions such as load-balancing based upon various statistics that aregathered by the controller. The CS also keeps track of statistics foreach flow and determines when a particular flow has become inactive. Atimer is associated with each flow and may be used to determine factorssuch as: most active flow, least active flow, time flow opened, mostrecent activity as well as other parameters related to flow statisticsand load balancing.

[0112] When a flow is detected as timed out, the CS sends a message tothe DFS to delete the flow (e.g. REAP). The DFS sends a message that isresponsive to the REAP indicating that either the flow is still active(e.g. STATS message with CONNALIVE set to true) or that the flow hasbeen deleted. The CS maintains the flow as active while waiting for theresponse from the DFS. The CS will either delete the flow from the CSflow tables or reset the timer for the flow after receiving the messagefrom the DFS.

[0113] A flow in the DFS may end before a TCP session ends.Consequently, the DFS may start a new flow for an existing TCP sessionand query the CS about it. The CS will be able to distinguish between anew DFS flow and a new TCP session by examining messages that arereceived from the DFS.

[0114] A new flow is detected when an event is detected by the DFS.Events that are detected by the DFS are communicated to the CS (ormultiple CSs) via the message bus (e.g. SSMB). In one example, a TCP orUDP connection-open is detected by the DFS indicating the start of a newflow.

[0115] There are several different types connections that can be openedusing TCP. Each type of connection results in an event that is detectedby the DFS, and requires a different response by the DFS. UDP flows arehandled similar to TCP events. The various connection open/close typeswill be discussed as follows below.

TCP Connection Open, Non-Application Proxy DFS-Assisted Virtual Servers

[0116] When a TCP connection open is detected of this type, the DFSsends a message (QUERRY) to the CS that contains the source anddestination IP addresses and port numbers. While the DFS awaits a replyfrom the CS, the DFS buffers all incoming packets in the flow(identified by its flow signature as described previously) until itreceives instructions from the CS. The CS will respond to the QUERRYwith a message (REPLY) describing translations to make for packets inthat flow, and information that will be used to switch the flow.

TCP Connection Open, Application Proxy Virtual Servers

[0117] When a TCP connection open is detected of this type, the DFSperforms a handshake with the client before proceeding. After a TCPhandshake proxy is made with the client, the DFS buffers packetsreceived from the client until the required data from the request isreceived. The DFS sends a message (e.g. APP_QUERY) to the CS thatcontains the source and destination IP addresses and ports as well asthe application data from the client request. The CS will respond to theAPP_QUERY with a REPLY message describing the translations to make forpackets in that flow, and information that will be used to switch theflow. Once the REPLY is received from the CS, the DFS performs ahandshake proxy with the server and establishes an outbound flow. TheDFS continues to buffer all packets in the flow until the TCP handshakeproxy with the server is completed, and the flow established.

TCP Connection Open, Raw Proxy Virtual Servers

[0118] When a TCP connection open is detected of this type, the DFSperforms a handshake with the client before proceeding. After a TCPhandshake proxy is made with the client, the DFS forwards (bridges)packets received from the client to the CS until the required amount ofpayload data is received. When the CS has received sufficient data tomake a load balancing decision, the CS will send a message (NEWFLOW) tothe DFS describing the translations to make for the packets in the flow.Once the DFS receives the NEWFLOW message, the DFS performs the TCPhandshake proxy with the server and establishes the outbound flow. TheDFS continues to buffer all packets in the flow until the TCP handshakeproxy with the server is completed, and the flow established.

TCP Connection Open, Hybrid CS-Assisted Virtual Servers

[0119] When a TCP connection open is detected of this type, the CSperforms a handshake with the client and receives data from the client.The CS continues to receive data from the client until sufficient datais received to make a load balancing decision. When the CS has made aload balancing decision, the CS will perform a TCP handshake with theserver and send a message (NEWFLOW) to the DFS describing thetranslations to make for the packets in the flow. Once the DFS receivesthe NEWFLOW message, the DFS will assume the flow, applying the TCPsequence number and offsets received in the NEWFLOW message, to thecontinuing packets in the flow.

TCP Connection Close

[0120] The DFS keeps track of the TCP connection termination protocolfor the flow (Application FIN, Server ACK, Server FIN, and ApplicationACK). The DFS should not delete a TCP flow when the flow is in themiddle of state transition. When a TCP connection close (or reset) isdetected, the DFS notifies the CS by sending a message (DELETE) to theCS. The DFS does not need to wait for a response from the CS and maystop tracking the flow. In a system that includes statistics gatheringmechanisms in the DFS, the DFS will include the statistics for the flowin the DELETE message.

DFS Message Processing

[0121] Messages received by the DFS from the CS are generally describedas shown in FIG. 20. Processing begins at start block 2010 and proceedsto block 2020 where the DFS begins parsing the received message. Whenthe message (e.g. REAP FLOW) from the CS is to delete a particular flow(as specified in the message), processing proceeds to block 2025, wherethe DFS updates the DFS tables based on flow activity (refer to theprevious discussion of FIG. 18). After the DFS flow activity is updated(either the flow is still alive, or deleted from the DFS table),processing is complete and processing ends at block 2080.

[0122] Returning to block 2020, processing proceeds to block 2030 whenthe received message is a message other than deleting a particular flow.At decision block 2030, the DFS determines if the received messageindicates a particular flow has timed out. When the message receivedfrom the CS indicates that the particular flow has timed out, processingproceeds to block 2025, where the DFS updates the DFS flow tables basedupon the activity of the particular flow. Processing proceeds from block2030 to block 2040 when the message received from the CS indicates thatthe message is not a flow timeout.

[0123] At decision block 2040, the DFS determines if the receivedmessage indicates a new flow is to be set up. When the message indicatesa new flow, processing proceeds to block 2045 where the new flow isprocessed. As discussed previously, new flows are processed inaccordance with routing/switching instructions that are provided by theCS, and entered into the DFS flow tables accordingly. When the messageis parsed as a message other than a new flow, processing proceeds fromblock 2040 to block 2050.

[0124] At decision block 2050, the DFS determines if the receivedmessage indicates to reset the system. When the system is to be reset,processing proceeds from decision block 2050 to block 2055 where allflows are deleted from the DFS flow tables. When the message does notindicate a system reset, processing proceeds from block 2050 to block2060.

[0125] At block 2060, the DFS determines that an invalid message hasbeen received. Alternatively, the DFS may process other message types asmay be required in a particular application. From block 2060, processingproceeds to block 2070 where processing is completed. Processing alsoproceeds to block 2070 from blocks 2025, 2045, and 2055.

[0126] One example of new flow processing (e.g. 2045 in FIG. 20) isshown in FIG. 21. Processing begins at start block 2110 and proceeds toblock 2120 where the DFS begins to parse the new flow instruction fromthe received CS message. The new flow has a corresponding flowsignature, destination, source as well as any other relevant routing orswitching information that is described by the CS in the receivedmessage. After the DFS extracts the relevant information from thereceived message, processing proceeds from block 2120 to block 2130.

[0127] At block 2130, the DFS determines if the new flow signaturecorresponds to an existing flow entry in the DFS tables. When the newflow signature is part of an existing flow entry, processing proceedsfrom block 2130 to block 2170 where the DFS flow table is updated. Whenthe new flow signature is not recognized by the DFS (not in the DFS flowtable), processing proceeds from decision block 2130 to decision block2140.

[0128] At decision block 2140, the DFS determines if the DFS flow tableis full. When the DFS flow table is full, processing proceeds to block2150 where the DFS creates a free space in the DFS flow table. The spacemay be made available by any appropriate criteria such as, for example,deleting the oldest flow signature entry. Processing proceeds from block2150 to block 2160 where the new flow signature is entered into the DFSflow table based upon the instructions provided by the CS. Processingalso proceeds to block 2160 from decision block 2140 when the DFS tableis not full. From block 2160, processing proceeds to block 2170 whereprocessing is concluded.

CS Message Processing

[0129] Messages received by the CS from the DFS are generally describedas shown in FIG. 22. Processing begins at start block 2210 and proceedsto block 2220 where the CS begins parsing the received message. At block2220 the CS determines if the received message is a request forinstructions (e.g. QUERY) related to a particular flow. When the messageindicates a request for instructions, processing proceeds from block2220 to block 2225. Otherwise processing proceeds from block 2220 toblock 2230. At block 2225, the CS analyzes the particular flow describedin the received message and determines how to the DFS is to handlerouting or switching the packets related to that flow. The CS may useany appropriate method to determine the routing/switching of packetssuch as, for example, based upon load balancing. The CS subsequentlysends a message (e.g. REPLY) to the DFS containing instructions forhandling the flow.

[0130] At block 2230 the CS determines if the received message is anapplication request for data from a server. When the message indicatessuch a request (e.g. AP_QUERY), processing proceeds from block 2230 toblock 2225. Otherwise processing proceeds from block 2230 to block 2240.

[0131] At block 2240 the CS determines if the received message is arequest from the DFS for a particular flow to be deleted from the CSflow tables. When the message indicates that the particular flow is tobe deleted (e.g. DELETE), processing proceeds from block 2240 to block2245. Otherwise, processing proceeds from block 2240 to block 2250. Atblock 2245, the CS deletes the particular flow from the CS flow table.

[0132] At block 2250, the CS determines if the received message is arequest from the DFS (or another CS) to reset the system. When themessage indicates a system reset (e.g. RESET), processing proceeds fromblock 2250 to block 2255. Otherwise, processing proceeds from block 2250to block 2260.

[0133] At block 2260, the CS determines that an invalid message has beenreceived. Alternatively, the CS may process other message types as maybe required in a particular application. From block 2260, processingproceeds to block 2270 where processing is completed. Processing alsoproceeds to block 2270 from blocks 2225, 2245, and 2255.

[0134] The logical operations of the various embodiments of theinvention are implemented as a sequence of computer implemented actionsor program modules running on one or more computing devices; and/or asinterconnected hardware or logic modules within the one or morecomputing devices. The implementation is a matter of choice dependent onthe performance requirements of the computing system implementing theinvention. Accordingly, the logical operations making up the embodimentsof the invention described herein are referred to alternatively asoperations, actions or modules. Program modules may be described as anyconstruct (e.g. routines, programs, objects, components, and datastructures) that perform particular tasks or implement particularabstract data types. The functionality of program modules may becombined or distributed in various embodiments.

[0135] The above specification, examples and data provide a completedescription of the manufacture and use of the composition of theinvention. Since many embodiments of the invention can be made withoutdeparting from the spirit and scope of the invention, the inventionresides in the claims hereinafter appended.

We claim:
 1. An apparatus for directing communications over a network, comprising: (a) a control component that receives a data flow requesting a resource and determines when the data flow is unassociated with a connection to a requested resource, wherein the control component associates a selected connection to the requested resource when the control component determines the data flow is unassociated with the connection to the requested resource; and (b) a switch component that employs the connection associated with the data flow to direct the data flow to the requested resource, wherein a capacity of the switch component and a capacity of the control component are independently scalable to support the number of data flows that are directed to requested resources over the network.
 2. The apparatus of claim 1 , wherein the control component employs a buffer to list each data flow that is associated with the connection to the requested resource.
 3. The apparatus of claim 1 , wherein the control component employs a table to list each data flow associated with the connection to the requested resource.
 4. The apparatus of claim 1 , wherein the control component categorizes a plurality of data packets for each data flow.
 5. The apparatus of claim 1 , wherein the control component determines when an event associated with the data flow occurs.
 6. The apparatus of claim 5 , wherein the control component categorizes each event.
 7. The apparatus of claim 1 , further comprising a flow signature that is associated with the data flow, the flow signature is compared to a set of rules for handling each data flow that is associated with the connection to the requested resource.
 8. The apparatus of claim 7 , wherein the flow signature includes information about a source and a destination for each data packet in the data flow.
 9. The apparatus of claim 7 , wherein the flow signature includes a timestamp.
 10. The apparatus of claim 1 , wherein the switch component collects metrics regarding each connection to each resource.
 11. The apparatus of claim 1 , further comprising a server array controller that includes the action of the control component and switch component.
 12. An apparatus for directing communications over a network, comprising: (a) a flow component that receives packets associated with a flow and switches each received packet associated with the flow to a connection; and (b) a control component that determines the connection based on information collected by the flow component, wherein the flow segment and the control segment are independently scalable to handle the number of data flows that are directed to requested resources over the network.
 13. The apparatus of claim 12 , wherein the control component performs control and policy enforcement actions for each flow.
 14. The apparatus of claim 12 , wherein the flow component collects information regarding each flow including metrics and statistics.
 15. The apparatus of claim 14 , wherein the control component performs load balancing for each flow based on the information collected by the flow component.
 16. The apparatus of claim 12 , further comprising a primary control component and a secondary control component, wherein a load is shared between the primary and secondary control components and when the primary control component is inoperative, the secondary control component takes over the actions of the primary control component and the flow component provides the state information for each flow.
 17. The apparatus of claim 12 , further comprising a server array controller that includes the control component and the flow component.
 18. The apparatus of claim 17 , wherein the server array controller includes an interface for internal and external networks.
 19. The apparatus of claim 12 , further comprising a flow signature that is associated with each flow.
 20. The apparatus of claim 12 , further comprising a timestamp that is associated with each flow, wherein the control component employs the timestamp to determine factors used for load balancing, the factors include most active, least active, time opened and most recent activity.
 21. The apparatus of claim 12 , further comprising a session that is associated with the flow, the session including TCP and UDP.
 22. The apparatus of claim 12 , wherein the control component determines when a new flow occurs based on the detection of an event.
 23. A method for directing communications over a network, comprising: (a) employing a control component to receive a data flow requesting a resource and determining when the data flow is unassociated with a connection to a requested resource, wherein a selected connection is associated with the requested resource when the data flow is unassociated with the connection to the requested resource; and (b) employing the connection associated with the data flow to switch the data flow to the requested resource, wherein the switching capacity and the control capacity are independently scalable to support the number of data flows that are directed to requested resources over the network.
 24. The method of claim 23 , further comprising sending state information as multicast messages and other information as point cast messages.
 25. The method of claim 23 , further comprising responding to messages that are authenticated.
 26. The method of claim 23 , further comprising employing a state sharing message bus (SSMB) between a switch and a control component.
 27. The method of claim 26 , further comprising layering the SSMB on top of a session, the session including TCP and UDP.
 28. The method of claim 26 , further comprising asynchronous and independent communication between the control component and the switch.
 29. The method of claim 23 , further comprising associating a flow signature with each flow.
 30. The method of claim 23 , further comprising comparing when the data flow is associated with the connection to the requested resource and when the interface component determines that the data flow is unassociated with the connection to the requested resource, wherein the comparison is employed to determine the data flow's association with the connection to the requested resource.
 31. An apparatus for directing communications over a network, comprising: (a) means for a control component that receives a data flow requesting a resource and determines when the data flow is unassociated with a connection to a requested resource, wherein the control component associates a selected connection to the requested resource when the control component determines the data flow is unassociated with the connection to the requested resource; and (b) means for a switch component that employs the connection associated with the data flow to direct the data flow to the requested resource, wherein a capacity of the switch component and a capacity of the control component are independently scalable to support the number of data flows that are directed to requested resources over the network. 